Surveillance video aided US officials in naming the two brothers, ethnic Chechens, as responsible for the attack.

Federal authorities have also charged three others with interfering with the investigation. The investigation is continuing, with the focus now on computer evidence as well as a trickle of information coming from Russian authorities.

Commissioner Davis said that surveillance images can be helpful to law enforcement as evidence and are aimed at protecting the public, not stifling freedom or chilling free speech.

"I do not endorse actions that move Boston and our nation into a police state mentality, with surveillance cameras attached to every light pole in the city," he added.

Committee Chairman Michael McCaul has said his panel will focus on how US efforts have evolved to address threats such as the bombing that are rarely seen in the United States but are more common in other countries.

Mr McCaul said he fears the Boston bombers may have succeeded because "our system failed." He said the US can and must do better.